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Updated: May 15, 2026
Measuring Microbial Mutation Rates with the Fluctuation Assay
Published on: November 28, 2019
Relationships between mutant prevention concentrations and mutation frequencies against enrofloxacin for avian
1National Veterinary Assay Laboratory, Ministry of Agriculture, Forestry and Fisheries, 1-15-1 Tokura, Kokubunji, Tokyo 185-8511, Japan. ozawa@nval.maff.go.jp
Abstract:
Clinical efficacies of mutant prevention concentration (MPC) and mutant selection window (MSW) hypotheses have been evaluated for human clinical isolates. We tested the MSW hypothesis by evaluating the relationships between MPCs and mutation frequencies against enrofloxacin for avian pathogenic Escherichia coli (APEC) isolates. Mutation frequencies of strains with MPC:MIC ratios of 8 to 16 were significantly higher than those of strains with an MPC:MIC ratio of 4. Mutation frequencies and MPCs of serogroup O2 strains were lower than those of the other strains; these results may correlate with the absence of fluoroquinolone-resistant O2 strains. Our results support the MSW hypothesis that the range of the MSW is involved in selection of resistant mutants.
